a) Field of the Invention
The invention is directed to an arrangement for fastening a length measurement device and can be used, for example, for combined positioning and measuring devices in machine tool construction and machine construction in general.
b) Description of the Related Art
Numerous positioning devices and measuring devices which enable the fastening of a length measurement device to a machine tool are known from the prior art. These positioning and measuring devices are completely independent units which are also manufactured separately (DE-C-27 12 421).
Normally, the guide of a base frame and the associated carriage or slide are mounted at the positioning device of a machine tool independently from one another and so as to be aligned separately relative to one another. In order for the measurement task to be properly carried out, special requirements and conditions must be met to bring the positioning device and measurement system into a working relationship. In particular, specially machined mounting faces must be provided at the machine, base bed, and slide. Also, special adjustment means are required for aligning the measurement system with respect to the operation of the slide. The mounting of the measurement system on the machine is very time-consuming.
Special mounting means in the form of a mounting rail for measurement systems is known from the company publication "NC Length Measurement Systems[NC-Langenme.beta.systeme]" by the Heidenhain company, April 1994. On the one hand, this mounting rail serves for mechanical stabilization and to compensate for thermal expansion between the base frame of the machine and the measurement system. On the other hand, after separate mounting on the base frame of the machine, a simplified mounting and a simplified exchange of the measurement system relative to the mounting rail can be achieved by means of this mounting rail. However, a disadvantage consists in that this mounting rail itself must be mounted on the machine in accordance with the same criteria as those of the unaccompanied measurement system and must be aligned with the guiding operation of the slide and in that the additional expensive mounting rail adds appreciably to the total cost.
Another type of measurement system is known from WO 90/02919. In this case, a self-adhesive steel-strip measurement rod is glued on the machine bed or base body via an applicator so as to be aligned with the guiding operation of the slide. A measurement system solution of this type is very costly in terms of assembly and the achievable basic accuracy of the measurement system is relatively inferior, since the inherent stability of the measurement strip is relatively poor and the measuring capability of the measurement rod deteriorates as a result of the slightest mechanical stresses or stress differences which are inevitable during the gluing-on process.